All TV transmitters (whether analogue or digital) have always been designed to ensure that viewers can get good reception if they've got a good quality EXTERNAL aerial. While some people have been able to get decent reception from indoor aerials that has never been the intention of broadcast engineers. (i.e. nobody has the right to complain about their signal quality if they're only using an indoor aerial).
If your boyfriend is getting GOOD (not just 'acceptable') analogue reception now [i.e. without any 'snow' on the screen] the chances are that he'll probably also get decent digital reception AFTER the digital changeover is COMPLETE. However the fact that he's still able to watch analogue TV shows that he's living in an area where the old analogue transmitters are still working. In those areas the digital transmitters are currently using reduced power (in order not to provide interference to the analogue transmissions), which means that there's currently much less chance of getting a usable signal with an indoor aerial. It might be best to wait until the switchover to digital is complete in his area (when he'll get full-strength digital signals). You can check when the analogue transmitters will be switched off here:
http://www.digitaluk.co.uk/when_do_i_switch
Chris